The present invention relates to an infra-red telemetry system, and in particular it relates to a telemetry system using infra-red radiation to transfer information between the rotor of a dynamoelectric machine and a fixed external location.
It is desirable, not only for testing but for continuous monitoring, to be able to transmit information between the rotor of a dynamoelectric machine and a stationary position externally of the machine while the machine is operating. For example, it is desirable to monitor the temperature at a number of specific locations on the rotor during start-up, continuous running and overload conditions. It may also be desirable to monitor voltage, current, relative displacement, strain, torque or flux density at locations on the rotor of a dynamoelectric machine.
Various systems have been developed for monitoring different variables on a rotating machine. One such system uses a radio link. An FM transmitter is mounted on the rotor and an FM receiver is mounted adjacent the machine. Thermocouples or other sensors are coupled to a modulating arrangement in the transmitter and the desired data is output at the receiver. The transmitter and receiver must have suitable antennae to obtain adequate signal transfer and this is sometimes a problem on a rotating machine part. In addition, the radio link is susceptible to interference and may create interference.
Another system for transferring information between a rotor and an external stationary position uses light-emitting diodes or LEDs. This system mounts the light sensitive detectors on the end of the shaft, concentrically with the axis of the machine and the LEDs are mounted directly in line and spaced from the end of the shaft. A pair of an LED transmitter and aligned detector represent one channel for information transfer. The LED and detector can be exchanged to transmit data in the other direction. An arrangement of this type is described in IBM Technical Disclosure Bulletin, Vol. 7, No. 10, March 1965 and entitled "Optical Information Coupling Between Stationary and Rotating Systems". It is, however, frequently not possible to have access to the end of a shaft of a dynamoelectric machine. For example, the shaft of a vertical water driven generator is normally not available for telemetry, and large motors may have loads and other equipment coupled to the ends of their shafts.
An alternate system spaces LEDs axially along the end of a rotor shaft and places photo sensitive detectors opposite them. For example, Canadian Pat. No. 965,840--Smith, issued Apr. 8, 1975 describes an information system for detecting ground faults in a field of a rotor. A fault energizes LEDs to a level which is detectable by the detectors to trip an alarm. This system is not intended to transmit data or variables, but only to indicate a single condition. Thus, it is not necessary to transmit information over a complete shaft rotation and the system is not intended to do this.